Fluorine-containing elastomers are molded into forms of an O-ring, a hose, a stem seal, a shaft seal and a diaphragm and are widely used in the fields of automobile industry, semiconductor industry and chemical industry because of their prominent heat resistance, chemical resistance, solvent resistance and fuel oil resistance.
However characteristics required therefor are becoming strict with progress of technology. In the fields of aeroplane and space, semiconductor manufacturing equipment, chemical plants and automobile industry, sealing property under higher temperature environment of more than 200° C. is demanded, and it is difficult to cope with such requirements in the cases of molded articles and sealing materials obtained by conventional methods of peroxide crosslinking and polyol crosslinking.
In the light of the mentioned problems, attempts to enhance characteristics required under high temperature environment by devising a crosslinking system have been proposed. For example, a curable composition comprising a perfluoro elastomer having a cyano group at its end and a nitrogen-containing nucleophilic compound and further a curable composition comprising an organotin compound as a curing agent (for example, cf. JP2004-500459A) are known. However in the case of the former composition, there is concern about toxicity and stimulant odor of a curing agent, and there is a problem with coloration of a molded article. In the case of the latter composition, there is a problem that tin used as a catalyst for triazine crosslinking has high toxicity.
In addition, a method of curing a perfluoro elastomer having a cyano group by exposing it to ammonia for a sufficient period of time (for example, cf. JP2003-531222A) is known. However this method has a problem that since the elastomer is exposed to ammonia being in the form of gas, it is difficult to uniformly cure a thick molded article stably.